1. Field of the Invention
The present invention relates to a receiver suitable for Wide band Code Division Multiple Access (W-CDMA) communication system compliant with 3rd Generation Partnership Project (3GPP).
2. Description of the Related Art
As a technology for implementing fast downlink for a W-CDMA communication system compliant with 3GPP currently being standardized, High Speed Downlink Packet Access (HSDPA) has been proposed (refer to 3GPP TS25.212 (v5.4.0)).
For HSDPA, a publicly known turbo coding/decoding method is used as an error correction method for send data. In the turbo encoding/decoding method, send data strings or information bits are encoded to create two kinds of check bit, a first check bit and a second check bit, for error correction processing. These two kinds of check bit are sent along with the information bits. The receiving side uses the received two kinds of check bit to perform error correction processing and reconstructs send data from the information bit.
The first check bits and the second check bits are reliability information of the information bits created in the turbo encoding processing by a sending side. Each of the first check bits and second check bits has a same amount of data as that of an information bit. Using these kinds of check bit for performing decoding processing by a receiving side can improve the precision of the reconstruction of the information bit.
In HSDPA, a sending side performs first rate match processing, interleave processing and second rate match processing. The first rate match processing thins out an amount of data of check bits in accordance with a buffer capacity of a receiving side after turbo-encoding. The interleave processing changes an order of data strings. The second rate match processing increases or decreases information bits and check bits so as to match an amount of data with a send frame. A receiving side reconstructs information bits and check bits by performing second rate dematch processing first and performing deinterleave processing and first rate dematch processing then. The second rate dematch processing is inverted processing of the second rate match processing. The deinterleave processing is inverted processing of the interleave processing. Information bits and check bits are reconstructed by performing first rate dematch processing. The first rate dematch processing is inverted processing of the first rate match processing. The reconstructed information bit and check bits are used to decode and reconstruct receive data by a turbo decoder.
In HSDPA, since an amount of data to be processed is dramatically increased from that of a conventional CDMA method, a required memory capacity may increase and processes are performed in parallel to reduce processing time. Thus, the size of the circuit tends to increase. Furthermore, since writing and/or reading are performed on a memory more frequently, data processing time and/or power consumption may increase.